Electronic apparatus for determining moisture content in materials



May 10, 1949. M. M BRAYER 2,469,736

' ELECTRONIC APPARATUS FOR DETERMINING MOISTURE CONTENT IN MATERIALS Filed Feb. 24, 1948 2 Sheets-Sheet 1 MflEV/A/ .L. fi fieeyae,

. INVENTOR.

BY I 18 M. 1.. M BRAYER ELECTRONIC APPARATUS FOR DETE May 10, 1949.

RMINING MOISTURE CONTENT IN MATERIALS 2 Sheets-Sheet 2 Filed Feb. 24, 1948 flier/Iv 11 [1 509752,

IN VEN TOR.

Patented May 10, 1949 STATES PATENT OFFICE ELECTRONIC APPARATUS FOR DETERMIN- ING MOISTURE CONTENT IN MATERIALS Marvin-.1. McB'rayer, Alhambra, Calif.

Application February 24, 1948, Serial No. 10,437 2' Claims. (01. 1 75-483) This invention relates generally to electronic apparatus for measurementtofi moisture content in materials, and, in a particular. illustrative embodiment, to such apparatus designed." especially for granular, shredded; or powd'ered'matjerials.

The invention may be regarded; asanimproVement in apparatus disclosed in Patent Number 2 343,340 to Robert L. Stevensand in. a preferred type of electronic circuit employed" therein disclosed in Patent Number 2,231,035 to Robert L. Stevens and James 1?; Dallas.

Briefly;. such apparatus employs a. high frequency vacuum tube oscillator having an output circuit leading to output electrodes spaced by a gap for an electric field, and the material Whose moisture contentisto be measured is placed in this field; The constants of the oscillator are such that a microammeter inits grid" circuit will give readings varying with the power absorbed by the materiaLfrom theoutput. circuit of the oscillator; and since the power absorption character'- istics of materials varywith this moisture content,, the microammeter' readings: indicate percentage of moisture content. Diflering materials have widely difiering power absorption characteristics; and; it necessary to adjust certain constants of the, circuit at the time of manufactureof the instrument to" match its sensitivity to the power loss characteristics of the material with which it is. to be used; given instrument is accordingly useful, ordi'naril'y;, only on a given material for which it has-been Standardized. It has therefore been necessary for those dealing with several materials of diverse characteristics to purchase one: entire moisture testing instrument for each. Particularly in the: case of inst'ruments for use with granular materials, which usually involve hydraulicmeansfor placingthe The invention" providesa; moisture measuring.

apparatushaving a quickly detachable and re-'- placeab'le component containing range-determining circuit elements of theosciilator; The-instrw ment maybe equipped with a number" of these components; each designed to adjust the oscillator to the proper range for a given. material,.

and these componentsmaybeinstantly" changed;

2 at will, depending upon calls made from time to time upon the instrument.

The invention also provides certain improvements in granular moisture testing equipment, as will appear in the course of the ensuing description.

The invention will be understood from the following. detailed description of presentillustrative embodments thereof, reference being had to the accompanying drawings, in which:

Figure 2 is a vertical section taken in accord'.

' ance with the plane 22 of Figure 1;

Figure 3 is a view taken in accordance with the line 33 of Figure 2;

Figure 4 is a vertical medial section through the material cup, electrode, and electrode holder, together with the upper end portion of the hydraulic plunger;

Figure 5 is a section taken on line 5-5 of Fig-. ure 4;.

Figure 6 is a perspective view of the removable unit, shown in. disassembled position with refer.- ence to its mounting panel;

Figure 6a is a fragmentary sectional. view showing a connector socket used'in the bottom of the removable component ofthe oscillator;

Figure 7 is a view similar to Figure 3, but showing a modification;

Figure 8 is a view of" themounting panel for the electronic unit,.t'o'gether withthe removable. range conversion unit shown in disassembled position; and

Figures 9 and 10 show two forms of electric circuit arrangement in accordance withthe in-.

vention.

In Figures 1 to 5 of the drawings, numeral Ill designates a lower or base housing, including heavy steel bottom or'base' plate I I, together with sheet metal sides and-top, as indicated. Mounted. directly on base plate" H is. a two-way hydraulic power unit or jack,v designated generally by numeral I2, and which may be of any conventional type suitable to the purpose, this particular jack having plunger l3 adapted to be elevated by reciprocating jack handle M, and the plunger being understood to be returnable by any conventional.

any suitable standard jack may be employed, no"

further description or illustration. of the, jack is deemed necessaryto an understanding of" the invention. It may be noted, however, that the top of the jack cylinder is flush with the top of the housing I8, and that the jack plunger It moves upwardly from the top of the housing to compress the material in the material cup, prior to making moisture measurements thereon. A pressure gage G adapted and connected to indicate the hydraulic pressure developed by this jack may be mounted in the front of housing I8, as indicated.

A plurality of heavy steel tie rods I1, here three in number, have reduced lower ends I8 threaded into base plate II, and these tie rods extend upwardly above the top of housing I8 to support an instrument housing 28 in vertically spaced relation above housing I8, as shown. An approximately triangular, suitably apertured plate I9 is moved down over tie rods I1 to rest on the top of box I8, and chromium-plated tubes 28 are then placed on the tie rods, with their lower ends engaging the plate I9. The lower wall of housing 28, as well as a heavy plate 2| mounted inside said wall, are apertured to receive the reduced screwthreaded upper end portions 22 of tie rods I1, and rest downwardly on the tie rod shoulders 23, being held in place by nuts 24 all as clearly shown in Figure 2.

A cylindrical steel material cup 38 is mounted on the upper end portion of jack plunger I3. This cup 38 has a bottom wall 3I which is formed with a detachable connection with the upper end portion of plunger I3, as shown best in Figures 4 and 5. The bottom wall 3I has a central aperture 33 defined by a flange 34 which is engageable in annular groove 36 formed around plunger I3 near the upper end thereof. The wall 3| is counterbored, as at 36, to accommodate the full diameter of the upper end portion or head 31 of plunger I3. It will be evident that the flange 34 on the cup causes the cup to be secured against vertical movement in either direction with reference to the plunger. To permit assembly and disassembly of the cup in relation to the plunger, the apertures or bores 33 and 36 in the cup are afforded lateral slots through to the outside of the cup, as indicated at 38. It will be evident that the cup may be disassembled from the plunger by moving it toward the left, as viewed in either of Figures 4 or 5, or may be assembled by moving it in the opposite direction.

In the bottom of cup 38 is a steel closure disc 48, preferably removable for ease of cleansing. The sample of material to be tested will be undestood to be placed inside the material cup prior to assembling the latter with the jack plunger I3, and such material is indicated in the cup at s in Figure 4.

Secured as by screws 44 to the aforementioned heavy plate 2| is a steel, cylindrically shaped electrode holder 45, the latter being receivable with a very close sliding fit inside the cylindrical bore of the material cup 38. The lower end of this holder 45 is recessed to receive insulation electrode disc 46, in the lower face of which are mounted, in flush positions, two annularly spaced electrode rings 41 and 48. These rings 41 and 48 are separated by an insulation cap, and, being energized by a high frequency electric current, produce an electric field which extends downwardly into the material sample s below the lower face of the electrode disc 46. The electrode plates 41 and 48 are energized by means of conductors 49 and 58 lead downwardly through a central bore Si in holder 45 and through suitable passageways in the disc 46 as indicated.

Mounted in housing 28, preferably at a short spacing above the bottom wall of said housing is an insulation platform 68, and mounted on and above said platform is an insulation panel 6I. This panel 6I carries a quick detachable unit 62 which includes certain range determining components of the electronic circuit of the apparatus.

Reference is next directed to Figure 9 showning a preferred electric circuit employed in the apparatus. This circuit comprises a high frequency vacuum tube oscillator including oscillator tube 18 (typically a 1LE3), having grid and plate circuits H and 12 coupled by grid and plate circuit coils 13 and 14, respectively, to which is coupled coil 15 of an output circuit which includes leads 16 and 11, the latter energizing the aforementioned electrode members 41 and 48 via wires 49 and 58. Plate circuit 12 includes lead 88 connecting the plate of tube 18 to coil 14, lead 8I connectingcoil 14 to by-pass condenser 82, and lead 83 connecting condenser 82 to filament ground lead 84.

Grid circuit 1I includes lead connecting the grid to coil 13, lead 86 connecting coil 13 to bypass condenser 81, and lead 88 connecting condenser 81 to ground filament lead 84. The positive terminal of the filament is connected by lead 98 to the positive terminal of A or filament battery 9I, the negative terminal of which is grounded. Lead 98 is also connected to the negative terminal of 15 volt B battery 92, the positive terminal of which is connected through fixed limit resistor 93, adjustable voltage divider resistor 94, and fixed resistor to the aforementioned ground lead 84. In laboratory apparatus, the A and B battery power supply may of course be replaced by a suitable power supply fed by commercial power mains. The variable tap of voltage divider resistor 94 is connected by lead 96 to plate circuit lead 8!. The voltage applied to the plate of tube 18 is that between circuit lead 96 and ground, and is under the control of voltage divider 94.

Positive grid bias voltage for the tube 18 is obtained from plate battery 92 through a resistor network leading to a connection with the grid circuit lead 86. Thus, a resistor I88 is connected at one end to plate circuit lead 96, and at its other end to one end of resistor I 8|, the other end of which is connected to ground lead 84. A lead I82 is connected from a point between resistors I88 and I 8|, and this lead I82 goes to a microammeter lead I 83 leading to microammeter M. The other microammeter lead I84 includes resistor I85, and connects to lead I86 leading to grid circuit lead 86. A resistor I81 is connected between leads I86 and 96, and a resistor I88 is shunted across meter leads I83 and I84.

Without setting any limitations on the invention, the various resistors may have approximate values as follows: Resistor 93, 2400 ohms; resistor 94, 3000 ohms; resistor 95, 10,000 ohms; resistor I88, 18,000 ohms; resistor IN, 1600 ohms; resistor I85, 680 ohms; resistor I88, 1300 ohms; resistor I81, one meg. The microammeter may have a resistance of 660 ohms.

In operation, the oscillator creates a high frequency oscillating field between the output electrodes 41 and 48, which field penetrates the material sample s in the material cup 38, it being understood that the material sample is under a predetermined compression by operation of the hydraulic jack. The material in this cup will absorb power from the electric field depending upon the amount of moisture present in the M, falls materially with increasing: power ab-- sorption fromthe. oscillator, and, therefore falls with increasing moisture content in the material on test: The reading of this microammeter ac-- cordingly-is a measure of the percentage moisture in the material.

Materials of various characteristics require electric fields of varying degrees of power and penetration. For some material requirements; a highly sensitive instrument is required; and for others; the sensitivity should be low. The circuit iseapableof being balanced" to almost any' requirement b-y adjustment of the relative values or the previously mentionedfixed resistors 03, 95, I00, IOI, I05, I01 and I08. If still further adjustment is required, the tube 10 and/or coils may be changed. The adjustment and balancing of these oscillator components is a factory operation, and once the circuit has been adjusted for a given material, it is useful only for that particular material. In accordance with the present invention, this network of resistors is placed within the quick detachable unit 62, mentioned hereinbefore. In the specific embodiment of Figures 1 to and 9, the unit 62 includes also the vacuum tube and oscillator coils and condensers, although in a later described embodiment, only the resistor network is included within the removable unit. Referring again to Figure 9, the parts within the removable unit 62 are seen to be enclosed within the dotted rectangle designated by numeral 62, and the parts outside the said rectangle, which includes the meter M, batteries SI and 92, voltage divider 94, and electrodes 41 and 48, are permanently mounted in the housing 20 separate of the unit 82. Detachable pin and socket connections, such as indicated at I20 and I2I, are made in the various leads connecting the electric components within the unit 62 and the remaining components permanently mounted in or on the instrument housing 20.

Referring again to Figures 1 to 3, the meter M will be seen to be mounted in the front wall of housing 20, the voltage divider 94 to be also mounted in the front wall of housing 20, and the batteries 9| and 92 to be mounted on platform 60 to the rear of the housing 20. The removable unit 62 may comprise a sheet metal housing I30 comprising sides, ends and top, and an insulation bottom wall I3I. Rising from the latter is an insulation panel I32 on which the various fixed resistors may be mounted. At one end, on an insulation platform I33, is mounted a coil assembly C understood to comprise the three coupled coils I3, 14 and I5, this assembly preferably being covered with an insulation compound as indicated at I34. Mounted above the coil assembly is the socket I 35 for the aforementioned oscillator tube 10. The bottom wall I3I has mounted therein a plurality of the aforementioned socket units I2I (Figure 6a for the coacting pin connectors I20 which are mounted on the panel 6|.

Thus, the apparatus may be equipped with a plurality of the removable units 62, replaceable with one another at will, and each adjusted in the factory or laboratory to match the range of the apparatus as a whole to some particular material with which it is to be used.

Figures 7, 8 and 10 show the modified embodiment referred to earlier, it being assumed in thisinstancez onlytheresistors; and not. the: tube m and coils, will: req re; adjustment. or substitu tions- Eor' convenience. corresponding. p -ts in; the twe embodiments will. be identified by corre- I spending numerals.

Referring first. toFigure 10, it will be seen' that. the circuit is, exactly the: same. as Figure 9;, execenting hat. only" the fixed resistors of the-oscile la er are included.- within the: removableunit,v designated; this instanceby the numeral 621.1,. and identified; in. figure 10 by the dotted; rec-- tangl Referring again to Figures 7 and 8, the; removable unit. 62a; is mounted at. one. end of:

insulation. panel 6.1;, bein connectable in circuit;

with the-oscillator by: pin. and socket;- connectors I'm-and I2I- of; the-same type as. explained incontnection. with theearlier'embediment. This re: movable unit- 62a again-has a sheet metal hous irrg, indicated: in this instance by numeral I40"... and the various resistorsmay be mounted, on, its insulation. base plate Mt as: indicated,-v it; being: understood that the plate MI; will have the proper connector sockets of the same type as shown in Figure 6a. The vacuum tube 10 and coil I34 may be mounted inside a second housing I42 also mounted on the panel GI, and these components will be understood to be wired up in accordance with the circuit diagram of Figure 10. Thus in the embodiment of Figures '7, 8 and 10, the removable range determining unit is reduced to the bare resistor network by which the range of the instrument is set in the factory. By equipping the instrument with a number of these removable network resistors, the instrument may .be adapted to any of a corresponding number of materials of diverse characteristics.

I claim:

1. In a moisture testing instrument for granular materials, the combination of a base frame member, a power unit mounted on said base frame member, said power unit having a vertically movable plunger, 2. material cap carried by said plunger, an upper frame member positioned over said cup, tie rods connecting said base frame member and said upper frame member, an electrode holder carried by and extending downwardly from said upper frame member in alinement with said cup, and being adapted to slidably receive said cup with a close working fit, an insulation block carried by the lower end of said holder, electrode means on said block adapted to contact a sample of material in said cup when said plunger is elevated, an instrument housing carried by said upper frame member, a vacuum tube oscillator mounted within said housing, said oscillator including a vacuum tube, power supply means, a meter sensitive to power output, a power output circuit connected to said electrode means, and resistor means for influencing the sensitivity of the oscillator, a quick detachable unit inside said housing carrying a portion of said oscillator including said resistor means, the members of said oscillator carried by said quick detachable unit having quick-break circuit connections with the members of the oscillator mounted in said housing separate of said removable unit.

2. In a moisture testing instrument for granu lar materials, the combination of a base frame member, a power unit mounted on said base frame member, said power unit having a vertically movable plunger, a material cup carried by said plunger, an upper frame member positioned over said cup, tie rods connecting said base frame member and said upper frame member, an electrode holder carried by and extending downward- 1y from said upper frame member in alinement with said cup, and being adapted to slidably receive said cup with a close working fit, an insulation block carried by the lower end of said holder, electrode means on said block adapted to contact a sample of material in said cup when said plunger is elevated, an instrument housing carried by said upper frame member, a vacuum tube oscillator mounted within said housing, said oscillator including a vacuum tube, power supply means, a meter sensitive to power output, a power output circuit connected to said electrode means, and resistor means for influencing the sensitivity of the oscillator, a plug-in unit insertable inside said housing, said unit carrying a portion of said oscillator including said resistor means, and pin and socket electric connector means mounting said unit inside said housing and serving to electrically connect the oscillator members inside said removable unit with the oscillator members mounted in said housing separate of said unit.

MARVIN L. MCBRAYER.

REFERENCES CITED The following references are of record in the file of this patent: 

